NEWTOWN, Conn. » A 20-year-old man wearing combat gear and armed with semiautomatic pistols and a semiautomatic rifle killed 26 people — 20 of them children — in an attack Friday at an elementary school in central Connecticut.

Witnesses and officials described a horrific scene as the gunman, with brutal efficiency, chose his victims in two classrooms while other students dived under desks and hid in closets.

Hundreds of terrified parents arrived as their sobbing children were led out of Sandy Hook Elementary School in a wooded corner of Newtown. By then all of the victims had been shot, and most were dead, and the gunman, identified as Adam Lanza, had committed suicide. The children who were killed were said to be 5 to 10 years old.

A 28th person, found dead in a house in the town, was also believed to have been shot by Lanza. That victim, one law enforcement official said, was Lanza’s mother, Nancy Lanza, who worked at the school. She apparently owned the guns he used.

A third weapon, a .223-caliber rifle, was found in the car, and more guns were recovered during the investigation.

The principal had buzzed Lanza in because she recognized him as the son of a colleague. Moments later she was shot dead when she went to investigate the sound of gunshots. The school psychologist was also among those who died.

The rampage was the nation’s second-deadliest school shooting, exceeded only by the 2007 Virginia Tech massacre, in which a gunman killed 32 people and then himself.

The gunman was chillingly accurate. A spokes­man for the state police said he left only one wounded survivor at the school. All the others hit by the barrage of bullets died, suggesting that they were shot at point-blank range. Lanza’s rifle was similar to a weapon widely used by troops in Af­ghani­stan and Iraq.

The Associated Press reported that a custodian ran through the halls, warning of a gunman on the loose, and someone switched on the intercom, alerting people in the building to the attack — and perhaps saving many lives — by letting them hear the hysteria going on in the school office, a teacher said. Teachers locked their doors and ordered children to huddle in a corner or hide in closets as shots echoed through the building.

Law enforcement officials offered no hint of Lanza’s motive and were trying to determine if he suffered from a personality disorder.

"I don’t think anyone knows the answers to those questions at this point," one investigator said.

FBI agents interviewed his brother, Ryan Lanza, in Hoboken, N.J. His father, Peter Lanza, who was divorced from Nancy Lanza, was also questioned, one official said.

At the White House, President Barack Obama struggled to read a statement. More than once he dabbed his eyes.

"I know there is not a parent in America who does not feel the same overwhelming grief that I do," Obama said.